Optimizing prosthetic socket function often comes with a bit of trial and error. Since no one has thoroughly studied what happens in the prosthetic socket during movement, prosthetists often deal with patient complaints by repeatedly modifying the socket based on the patient’s feedback. However, researchers believe there is a better way to refine prosthetic sockets.
Currently, the challenge of creating a comfortable prosthetic socket lies in having no existing data on how prosthetic socket design affects in-socket mechanics, as well as how in-socket mechanics affect the user’s comfort and function. But prosthetists believe that limiting motion in the residual limb and the skin around it will improve socket function.
The challenge is to gather data on how socket design can reduce these movements and confirm that reducing motion in the residual limb and skin will improve user comfort. Therefore, researchers felt the need to conduct a new study.
Although the market is saturated with prosthetic sockets marketed for above-knee amputees, all are designed from a cast of the residual limb. The problem is the cast doesn’t account for soft tissue deformation and regions of high loading, which develop during dynamic activities like walking. The result of these mass-produced, cast-molded prosthetic sockets is a whole host of problems for the prosthetic user, such as chronic skin problems, pressure ulcers, and an overall decreased quality of life.
The traditional socket optimization process
The current practice of optimizing a prosthetic socket’s fit and function relies on user feedback. It’s a repetitive process that is also dependent on the preferences and experience of the prosthetist.
Although the process is based on user-specific feedback, most prosthetists adhere to generally agreed-upon principles with various approaches. For example, if a patient complains about a local pressure point, one prosthetist may narrow the socket around the tricky spot to properly redistribute the contact force. Another prosthetist may widen the socket in the problematic area to relieve the pressure. It depends on the prosthetist’s interpretation of the issue, not hard data.
Researchers believe there is a data-based way to help prosthetists better interpret the situation.
The study will be conducted at the University of Pittsburgh, Pennsylvania. Recruitment of study participants began in September 2021, and its estimated completion is in December 2023. Study participants will be recruited from the local limb loss population.
This study will be built on the findings of prior research done on 12 above-knee amputees. In that study, the researchers measured the motion of the residual bone and the extent of deformation of the skin within the prosthetic socket while walking for three steps. They collected information using dynamic biplanar radiography, which is known for providing highly accurate data.
After lab testing, researchers performed a CT scan on the residual thigh; the scan was then used to create a participant-specific 3D model of the residual femur.
The researchers found that the residual limb skin is stretched rapidly during the late swing phase, when the leg is extended BEFORE the foot comes in contact with the ground. This is also when the prosthetic limb pulls on the residual limb.
The researchers were surprised that the findings contradict the prevailing assumption that the skin is most strained AFTER foot strike. The results highlight the need for measuring what happens within the prosthetic socket during movement.
The new study is currently ongoing. Besides seeking to understand how what happens inside the prosthetic socket relates to user-reported comfort and function, the researchers also aim to help streamline the design process of prosthetic sockets and evaluate the cost and efficacy of a new, data-informed prosthetic socket optimization process.
What do you think of this new study? What challenges do you encounter when wearing your prosthetic socket?